The Collaborative International Dictionary of English v.0.48:

Tuesday \Tues"day\ (t[=u]z"d[asl]; 48), n. [OE. Tewesday, AS.
   Tiwes d[ae]g the day of Tiw the god of war; akin to OHG. Zio,
   Icel. T[=y]r, L. Jupiter, Gr. Zey`s;, cf. OHG. Ziostac
   Tuesday, G. Dienstag, Icel. T[=y]sdagr. [root]244. See
   Deity, Day, and cf. Jovial.]
   The third day of the week, following Monday and preceding
   Wednesday.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Tuesday
    n 1: the third day of the week; the second working day [syn:
         Tuesday, Tues]